The present invention relates to a process for preparing a stabilized form of antibiotic compounds, in particular a carbapenem antibiotic composition.
Betalactams, a broader class of antibiotics which is further defined as carbapenems are useful for the treatment of infectious diseases including gram positive and negative, and aerobic and anaerobic bacteria. Carbapenems were first isolated from fermentation media in 1974 and were found to have broad-spectrum antibacterial activity. Since this discovery substantial investigations have been made into new carbapenem derivatives and many hundreds of patents and scientific papers have been published. The commercially marketed carbapenem is imipenem (N-formimidoyl thienamycin), which has a broad range of antibacterial activity. This compound can be used in the treatment of any disease that is conventionally treated with antibiotics, for example in the treatment of bacterial infection in mammals including humans.
It has been reported that dimerization of carbapenem is inhibited via the formation of a reversible equilibrium adduct between carbon dioxide and monosodium salt of carbapenem compound as shown below, where Ka and Keq are equilibrium constants of the reactions. 
During the manufacture of bulk antibiotic products such as carbapenem antibiotic, the pharmaceutical compound is prepared by chemical synthesis from raw materials in large quantities. Carbapenem antibiotic compounds are prepared in large batches as salt form, monosodium salt as shown above, which are weak crystalline solids, hygroscopic at ambient conditions, and unstable at room and refrigerated temperatures. Because the compound is unstable at a temperature above about xe2x88x9220xc2x0 C., the bulk compounds must be stored at a low temperature (about xe2x88x9220xc2x0 C.) to prevent degradation into dimers or open ring by-products. Although the unstable compound of carbapenem, after bulk manufacturing, can be stored for long periods of time at a low temperature, it must be converted into a stable formulation prior to use as once-a-day antimicrobial agent for intravenous (IV) or intramuscular (IM) administration.
Several reported cases for preparing carbapenem antibiotic compounds have shortcomings of teaching how to achieve a stable form of carbapenem antibiotics in its final formulation and manufacturing process. In particular, they fail to teach how to achieve the conversion of salt-containing carbapenem compound to a formulation exhibiting acceptable levels of degradates required for solid state and reconstitution stability for dosing to patients.
For example, Almarsson et al. (WO 98/18800) discloses a method for stabilizing carbapenem antibiotics by carboxylating the pyrrolidinyl amino acid with a carbon dioxide source, but fails to teach the steps necessary to obtain the stable form of carbapenem during its formulation process.
Zimmerman et al. (U.S. Pat. No. 5,952,323) relates a method of stabilizing a carbapenem compound by incorporating carbon dioxide source, but it also does not provide how to achieve the stabilized form of carbon dioxide adduct in its final composition.
In light of the above, an objective of the present invention is to provide a process for formulating a final product of stable antibiotic compound, in particular carbapenem antibiotic for the treatment of infectious diseases which include gram positive and negative, and aerobic and anaerobic bacteria. Another object of the present invention is to provide a novel manufacturing process to prepare the final formulation product of carbapenem antibiotic with acceptable levels of degradates, solid state stability and solution stability for dosing.
The present invention is directed to a process for preparing a final formulation product of a compound of Formula I, 
or its pharmaceutically acceptable salt, hydrate or solvate wherein,
R1 is:
(a) 1-hydroxyethyl,
(b) 1-fluoroethyl, or
(c) hydroxymethyl;
R2 and R3 are independently:
(a) hydrogen, or
(b) (C1-C6)-alkyl;
R4, R5 and R6 are independently
(a) hydrogen
(b) (C1-C6)-alkyl, or
(c) alkali-metal or alkali earth-metal wherein the alkali-metal or alkali earth-metal is sodium, potassium, lithium, cesium, rubidium, barium, calcium or magnesium; and
R7 and R8 are independently:
(a) hydrogen,
(b) halo,
(c) cyano,
(d) (C1-C6)-alkyl,
(e) nitro,
(f) hydroxy,
(g) carboxy,
(h) (C1-C6)-alkoxy,
(i) (C1-C6)-alkoxycarbonyl,
(j) aminosulphonyl,
(k) (C1-C6)-alkylaminosulphonyl,
(l) di-(C1-C6)-alkylaminosulphonyl,
(m) carbamoyl,
(n) (C1-C6)-alkylcarbamoyl,
(o) di-(C1-C6)-alkylcarbamoyl,
(p) trifluoromethyl,
(q) sulphonic acid,
(r) amino,
(s) (C1-C6)-alkylamino,
(t) di-(C1-C6)-alkylmino,
(u) (C1-C6)-alkanoylamino,
(v) (C1-C6)-alkanoyl(N-(C1-C6)-alkyl)amino,
(w) (C1-C6)-alkanesulphonamido, or
(x) (C1-C6)-alkyl-S(O)n wherein n is 0-2;
comprising the steps of:
(1) charging a solution of carbon dioxide source having a pH range of about 6.0 to about 12.0 into a reaction vessel;
(2) adding an effective amount of a mole ratio of a base and an active ingredient into the reaction vessel containing the solution of carbon dioxide source to maintain pH at about 6.0 to about 9.0 and a temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C.;
(3) lyophilizing the solution of Step (2) to yield the final formulation product of a compound of formula I with less than about 10% of moisture content.
The present invention relates to a process for preparing a stable form of carbapenem compound in its formulation and manufacturing processes. More specifically, the present invention involves a process for preparing a stabilized carbon dioxide adduct of carbapenem antibiotic by incorporating suitable carbon dioxide source to unstable salt form of carbapenem antibiotic, in particular monosodium salt of carbapenem, at suitable reaction conditions. The stable carbon dioxide adduct of the carbapenem antibiotic formulation is useful for the treatment of bacterial infections in mammal patients, which can be administered intravenously or intramuscularly.
The present invention is directed to a process for preparing a final formulation product of a compound of Formula I, 
or its pharmaceutically acceptable salt, hydrate or solvate wherein,
R1 is:
(a) 1-hydroxyethyl,
(b) 1-fluoroethyl, or
(c) hydroxymethyl;
R2 and R3 are independently:
(a) hydrogen, or
(b) (C1-C6)-alkyl;
R4, R5, and R6 are independently
(a) hydrogen
(b) (C1-C6)-alkyl, or
(c) alkali-metal or alkali earth-metal wherein the alkali-metal or alkali earth-metal is sodium, potassium, lithium, cesium, rubidium, barium, calcium or magnesium; and
R7 and R8 are independently:
(a) hydrogen,
(b) halo,
(c) cyano,
(d) (C1-C6)-alkyl,
(e) nitro,
(f) hydroxy,
(g) carboxy,
(h) (C1-C6)-alkoxy,
(i) (C1-C6)-alkoxycarbonyl,
(j) aminosulphonyl,
(k) (C1-C6)-alkylaminosulphonyl,
(l) di-(C1-C6)-alkylaminosulphonyl,
(m) carbamoyl,
(n) (C1-C6)-alkylcarbamoyl,
(o) di-(C1-C6)-alkylcarbamoyl,
(p) trifluoromethyl,
(q) sulphonic acid,
(r) amino,
(s) (C1-C6)-alkylamino,
(t) di-(C1-C6)-alkylmino,
(u) (C1-C6)-alkanoylamino,
(v) (C1-C6)-alkanoyl(N-(C1-C6)-alkyl)amino,
(w) (C1-C6)-alkanesulphonamido, or
(x) (C1-C6)-alkyl-S(O)n wherein n is 0-2;
comprising the steps of:
(1) charging a solution of carbon dioxide source having a pH range of about 6.0 to about 12.0 into a reaction vessel;
(2) adding an effective amount of a mole ratio of a base and an active ingredient into the reaction vessel containing the solution of carbon dioxide source to maintain pH at about 6.0 to about 9.0 and a temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C.;
(3) lyophilizing the solution of Step (2) to yield the final formulation product of a compound of formula I with less than about 10% of moisture content.
A preferred embodiment of the present invention is a process for preparing a formulation of a compound of Formula Ia, 
or its pharmaceutically acceptable salt, hydrates or solvate wherein,
R4, R5, and R6 are independently:
(a) hydrogen
(b) (C1-C6)-alkyl, or
(c) alkali-metal or alkali earth-metal wherein the alkali-metal or alkali earth-metal is sodium, potassium, lithium, cesium, rubidium, barium, calcium or magnesium;
comprising the steps of:
(1) charging a solution of carbon dioxide source having a pH range of about 6.0 to about 12.0 into a reaction vessel;
(2) adding an effective amount of a mole ratio of a base and an active ingredient into the reaction vessel containing the solution of carbon dioxide source to maintain pH at about 6.0 to about 9.0 and a temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C.;
(3) lyophilizing the solution of Step (2) to yield the final formulation product of a compound of formula I with less than about 10% of moisture content.
An aspect of the process as recited above is where the carbon dioxide source is selected from the group consisting of carbon dioxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, calcium carbonate, cesium carbonate, magnesium carbonate, lithium carbonate, and a mixture thereof. The preferred carbon dioxide source is sodium bicarbonate.
Another aspect of the process recited above is where the carbon dioxide source in Step (1) is present in an amount relative to the amount of active ingredient, wherein a mole ratio of carbon dioxide source to the active ingredient is about 0.5 to about 1.5, preferably about 0.8 to about 1.2.
Yet another aspect of the process as recited above is where the pH range in Step (1) is about 7.0 to about 9.0.
Still another aspect of the process as recited above is where a temperature range in Step (1) is about xe2x88x923xc2x0 C. to about 15xc2x0 C.
Still another aspect of the process as recited above is where the active ingredient is a compound of formula (a), 
wherein R1, R2, R3, R4, R7 and R8 are as defined above.
Still another aspect of the process as recited above is where the preferred active ingredient is a compound of formula (a)xe2x80x2
Another aspect of the process as recited above is where the base is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, calcium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxide, lithium tert-butoxide, sodium tert-butoxide and potassium tert-butoxide.
Yet another aspect of the process as recited above is where the base is sodium hydroxide at a concentration range of about 1N to about 3N.
Still another aspect of the process as recited above is where the effective amount of a mole ratio of a base to an active ingredient in Step (2) is about 0.7 to about 1.0.
Still another aspect of the process as recited above is where the mole ratio of a base to an active ingredient in Step (2) is about 0.8 to about 0.9.
Still another aspect of the process as recited above is where the pH range in Step (2) is about 7.0 to about 8.0.
Still another aspect of the process as recited above is where the temperature range in Step (2) is about xe2x88x921xc2x0 C. to about 5xc2x0 C.
Still another aspect of the process as recited above is where the base is added followed by the addition of the active ingredient in Step (2).
Still another aspect of the process as recited above is where the temperature range in Step (2) is about xe2x88x921xc2x0 C. to about 5xc2x0 C.
Still another aspect of the process as recited above is where the Step (2) further comprises a titration of the solution using a titrating agent to maintain the pH of the solution at a range of about 6.5 to about 8.5.
Still another aspect of the process as recited above is where the titrating agent is selected from the group consisting of sodium hydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, magnesium hydroxide, lithium methoxide, sodium methoxide, potassium methoxide, calcium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxide, lithium tert-butoxide, sodium tert-butoxide and potassium tert-butoxide.
Still another aspect of the process as recited above is where the moisture content of the final formulation product is less than about 5%.
Still another aspect of the process as recited above is where the step (3) initially further comprises the following steps of:
(a) filtering the final formulation product into a receiving vessel using a sterilizing filter;
(b) aseptically filling the filtered final formulation product into a sterile vial; and
(c) placing a lyophilization stopper on the filled sterile vial containing the final formulation product.
It is further understood that the substituents recited above would include the definitions recited below, and unless otherwise stated or indicated, the definitions shall apply throughout the specification and claims.
As used herein, the term xe2x80x9calkylxe2x80x9d includes those alkyls of a designated number of carbon atoms of either a straight, branched or cyclic configuration. Examples of xe2x80x9calkylxe2x80x9d includes but are not limited to: methyl (Me), ethyl (Et), propyl, butyl, pentyl, hexyl, heptyl, octyl, nonanyl, decyl, undecyl, dodecyl, and the isomers thereof such as isopropyl (i-Pr), isobutyl (i-Bu), sec-butyl (s-Bu), tert-butyl (t-Bu), isopentane, isohexane, and the like.
The term xe2x80x9calkoxyxe2x80x9d represents an alkyl group of indicated number of carbon atoms attached through an oxygen bridge, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, tert-butoxy, pentoxy, and the like.
The term xe2x80x9chalogenxe2x80x9d or xe2x80x9chaloxe2x80x9d refer to fluorine, chlorine, bromine and iodine.
As used herein, the term xe2x80x9c1 mole equivalentxe2x80x9d is defined as 1 mole of carbon dioxide source per 1 mole of active ingredient (or active drug), wherein carbon dioxide source includes carbon dioxide, sodium bicarbonate, potassium bicarbonate, sodium carbonate, potassium carbonate, calcium carbonate, cesium carbonate, magnesium carbonate, lithium carbonate, and a mixture thereof.
The term xe2x80x9cactive ingredient,xe2x80x9d also refers to as xe2x80x9cbulk drug,xe2x80x9d xe2x80x9cbulk active drug,xe2x80x9d xe2x80x9cbulk active beta-lactamxe2x80x9d or xe2x80x9cbulk active carbapenem,xe2x80x9d refers to the amount of actual unstable, beta-lactam, carbapenem and/or alkali-metal salt or alkali earth-metal salt containing carbapenem removed from cold storage. The preferred active ingredient is a compound of formula of (a), 
wherein
R1 is:
(a) 1-hydroxyethyl,
(b) 1-fluoroethyl, or
(c) hydroxymethyl;
R2 and R3 are independently:
(a) hydrogen, or
(b) (C1-C6)-alkyl;
R4, R5, and R6 are independently
(a) hydrogen
(b) (C1-C6)-alkyl, or
(c) alkali-metal or alkali earth-metal wherein the alkali-metal or alkali earth-metal is sodium, potassium, lithium, cesium, rubidium, barium, calcium or magnesium; and
R7 and R8 are independently:
(a) hydrogen,
(b) halo,
(c) cyano,
(d) (C1-C6)-alkyl,
(e) nitro,
(f) hydroxy,
(g) carboxy,
(h) (C1-C6)-alkoxy,
(i) (C1-C6)-alkoxycarbonyl,
(j) aminosulphonyl,
(k) (C1-C6)-alkylaminosulphonyl,
(l) di-(C1-C6)-alkylaminosulphonyl,
(m) carbamoyl,
(n) (C1-C6)-alkylcarbamoyl,
(o) di-(C1-C6)-alkylcarbamoyl,
(p) trifluoromethyl,
(q) sulphonic acid,
(r) amino,
(s) (C1-C6)-alkylamino,
(t) di-(C1-C6)-alkylmino,
(u) (C1-C6)-alkanoylamino,
(v) (C1-C6)-alkanoyl(N-(C1-C6)-alkyl)amino,
(w) (C1-C6)-alkanesulphonamido, or
(x) (C1-C6)-alkyl-S(O)n wherein n is 0-2;
The most preferred active ingredient is a compound of formula of (a)xe2x80x2, 
The term xe2x80x9cactive drug,xe2x80x9d as used herein, is defined as the actual amount of beta-lactam, unstabilized and stabilized carbapenem, and alkali metal salt-containing carbapenem and carbon dioxide-containing carbapenem.
The term xe2x80x9cquantum sufficitxe2x80x9d (xe2x80x9cq.s.xe2x80x9d), as used herein, is defined as the amount of a reagent necessary to increase the batch weight or volume to a specified total. As an example, a q.s. of 95% by wt % means the amount of reagent required to bring the weight percent up to 95% by weight based on 100% total weight.
The term xe2x80x9csolid state stabilityxe2x80x9d is defined as the ability of finished solid and lyophilized formulation (a porous off-white cake) at the end of about 2 years to deliver the prescribed and labeled dosage of active drug.
The term xe2x80x9creconstitution stabilityxe2x80x9d is defined as the ability of a solution prepared by the finished solid and lyophilized formulation into an appropriate diluent (i.e. 0.9% saline for injection, 1% Lidocaine, and etc.) to deliver the prescribed and labeled dosage of active drug.
The batch-wise process of the present invention is carried out under aseptic conditions and requires several reagents and processing units to prepare formulations of high pharmaceutical quality. The present process provide a high rate conversion from the alkali metal salt, such as monosodium salt of carbapenem to the carbon dioxide adduct and the low by-product formation, such as dimers and open ring compounds. The reaction parameters and conditions such as the mole ratio of carbon dioxide source and active ingredient, mole ratio of base and active ingredient (active bulk carbapenem), reaction temperatures, pH of the solution, proper mixing, and appropriate lyophilization parameters are critical to obtain a final formulation product of high pharmaceutical quality.
The process for preparing a stable intravenous formulation of a carbon dioxide adduct of a carbapenem requires the processing temperature of about xe2x88x923xc2x0 C. to about 15xc2x0 C., preferably about xe2x88x921xc2x0 C. to about 5xc2x0 C., and the pH of the pre-lyophilized active solution to be about 6.0 to about 12.0, preferably about 7.0 to about 9.0. The process is carried out under aseptic conditions. All reagents used during the present processes meet United States Pharmacopeia and National Formulary standards unless otherwise stated.
Methods of preparing the compound of the present invention are illustrated in the following process and examples. They are provided for illustrative purposes and should not be construed as limiting the invention disclosed herein.
PROCESS
Sodium hydroxide solution of about 1N to about 3N is prepared by dissolving a sufficient amount of sodium hydroxide NF pellets in a sufficient amount of Water For Injection (WFI). While adding the sodium hydroxide, the solution is constantly mixed to ensure complete dissolution. The compounder/reactor (200L stainless steel jacketed vessel) is jacketed and cooled to maintain at a low temperature to prevent bulk drug degradation during the process. A variable agitation system is attached to the compounder/reactor to ensure complete dissolution of the bulk drug into solution. Generally, about 40% by weight or 60% by volume of WFI is charged into the compounder/ reactor to begin the process, and the water is cooled to the temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C., preferably about xe2x88x921xc2x0 C. to about 5xc2x0 C. To measure the pH of the solution in the compounder/reactor, appropriate pH and temperature devices are used. The pH meter is typically calibrated with buffer solution of pH 7.0 and 10.0. To maintain the pH of the solution within the required range during the batch-wise process, an appropriate pH controller system equipped with a pump is utilized to meter sodium hydroxide solution into the compounder/reactor.
After the WFI in the compounder/reactor is cooled, mixing is commenced to prevent localization of pH, temperature, and concentration of reagents and bulk antibiotic drug. A sufficient amount of carbon dioxide source such as sodium bicarbonate and/or sodium carbonate is added to the compounder/reactor under continuous mixing of the WFI to provide a final formulation concentration of about one mole equivalent (a mole ratio of carbon dioxide source to the active ingredient is about 0.5 to about 1.5, preferably about 0.8 to about 1.2). The solution is mixed until the carbon dioxide source, such as carbonates are completely dissolved. The pH of the solution is measured to ensure that it is about 6.0 to about 12.0, preferably about 7.0 to about 9.0 at a temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C. It is preferred that the temperature and pH of the solution be confirmed prior to beginning the addition of bulk drug. The unstable bulk carbapenem drug is removed from a refrigerated unit held at about xe2x88x9220xc2x0 C. or lower and may be thawed to a temperature of from about 5xc2x0 C. to about 25xc2x0 C. for about 1 hour. A sufficient amount of the bulk drug is weighted out to provide a final formulation concentration of carbapenem to be about 200 g of active drug (as free acid)/liter formulation.
During the addition of the bulk active carbapenem to the compounder/reactor, the carbonate solution is constantly mixed. Generally, the mixing begins at lower agitation speed during the initial addition of bulk drug to the solution and as the amount of bulk in the solution is increased, mixing may be increased proportionally thereto. The primary purpose of mixing is to ensure complete dissolution of the bulk drug into the solution. As necessary, sodium hydroxide solution is added to the compounder/reactor during the addition of the bulk drug to maintain the pH of the solution to be about 6.0 to about 9.0, preferably about 7.0 to about 8.0. The bulk drug is generally slowly added to the compounder/reactor at a constant rate for about 30 minutes to about 90 minutes to enhance dissolution. At the end of the bulk drug addition, the solution is mixed for additional few minutes to ensure complete dissolution. The q.s. of the batch weight is adjusted to about 95% by weight of the final weight of the formulation with WFI, if needed, while maintaining the temperature at about xe2x88x921xc2x0 C. and about 5xc2x0 C. Further titration using sodium hydroxide may be performed over a 10 minute to 20 minute period to ensure a mole ratio of base (NaOH) and bulk active drug to be in the range of from about 0.7 to about 1.0, preferably about 0.8 to about 0.9. Finally, the batch is adjusted to 100% by weight of its final weight with WFI with moderate mixing.
Afterwards, the solution is filtered through a sterilizing filter such as that from about 0.2 xcexcm to about 0.25 xcexcm. When making larger batches, generally from about 10L to about 200L in a compounder/rector, the compounding vessel is sealed and pressurized to initiate filtration. Filtration can be done either by pumping the solution through sterilizing filters with an appropriate pump in the absence of compounding vessel that can be pressurized or appropriate gas to carry out filtration by pressure. The receiving vessel should be sterile and cooled to a temperature range of about xe2x88x923xc2x0 C. to about 15xc2x0 C. The density of the filtered formulation solution is generally about 1.0 g/mL to about 1.2 g/mL at about 0xc2x0 C. to about 5xc2x0 C., typically about 1.1 g/mL. Lyophilization of the completed formulation is preferred to simplified manufacture. However, the solution could be bulk lyophilized and the resulting powder filled into packages for use. If the processed by lyophilization in vials, the filtered formulation can be filled into vials and partially sealed with dry sterile siliconized lyophilization stoppers. In the following examples conventional 20 mL vials and 15 mL ADD-Vantage(trademark) vials are utilized. The vials are filled at specified target fill and then placed onto lyophilizer shelves, which are pre-cooled to a temperature of about xe2x88x9240xc2x0 C. to about xe2x88x9245xc2x0 C., typically about xe2x88x9240xc2x0 C. Suitable lyophilization cycle is then run with vials.
The lyophilization cycles used herein for the different vials are described in the examples below. Generally, the cycle requires the vials to be soaked at about xe2x88x9240xc2x0 C. for about two hours and then heated to a temperature range of about xe2x88x9225xc2x0 C. to about xe2x88x9215xc2x0 C. shelf temperature at a rate of about 0.5xc2x0 C./minute. The temperature is normally maintained at about xe2x88x9225xc2x0 C. to about xe2x88x9215xc2x0 C., and the pressure of the lyophilizer chamber is maintained at about 80 mTorr for about 48 hours to about 60 hours. The vials are heated to about 10xc2x0 C. shelf temperature at a rate of about 0.1xc2x0 C./minute and then to about 40xc2x0 C. shelf temperature at a rate of about 0.5xc2x0 C./minute, and maintained at 40xc2x0 C. for up to about three hours at a pressure of about 80 mTorr or lower. The vials are then heated to about 60xc2x0 C. shelf temperature at a rate of about 0.5xc2x0 C./minute and held there at about 80 mTorr or less for about 3 hours to about 10 hours. The shelves are then cooled to ambient temperature (about 20xc2x0 C.-30xc2x0 C.). The vials are completely sealed under a partial vacuum of about 0.9 bar/700 Torr or lower before removing them from the lyophilizer. The vials are stored at a temperature not exceeding about 25xc2x0 C. until needed.